The most I know is that ISO-10646 is an international standard,
proposed by public national organizations of many countries, and
Unicode is a "standard based in" or ¿implementation of? ISO-10646,
proposed by major American (United States) private organizations.

Not in Unicode site nor in other sites related to these standards
have i found a satisfactory answer.

Following http://www.unicode.org/ one finds:
<< The Unicode Standard is a subset of and code for code identical
to the International Standard ISO/IEC 10646-1:1993 >>